Can someone explaing to me the purpose of kamagong as a training tool?

I don't quite understand why a person would use kamagong sticks as a training tool in FMA instead of rattan. From what I understand, kamagong is more brittle than rattan and doesn't last as long when used frequently, which is a common trait amongst hardwoods. The only time I could really see kamagong being used is the scenario that ChiliPepper was talking about in the Sikh martial arts thread where they sparred using the hardwood because they wanted to use a tool that really hurts.

As mentioned, kamagong is like using a weight. its great for non contact drills. I've snapped a kamagong stick over a tire so I'm cautious about using them for contact. a guy I know uses a kamagong stick wrapped with duct tape and tennis racquet tape for Moro Moro (a contact drill). I think its good arm conditioning going against a kamagong stick but it shreds my rattan. if I used a kamagong stick too it would probably be a recipe for disaster.

Do you know if Indian-club/clubbell/mace exercises are the same movements as FMA drills, or are there different swinging movements involved?

Some of the twirlings are the same, and 1-2 of the Indian club exercises resembles a sinawali pattern, but in general they are different, for several reasons:
-club swinging focuses on the use of a heavy club, rather than a comparatively light stick or blade

-club swinging is exercise oriented, while FMA is fighting oriented. The exercise approach allows for a lot more diversity of movement; there are patterns unrelated to fighting in any way, and I think that's a good thing.

-a martial approach to swinging clubs tends to dictate that the club moves first, then the arm, then the body, as not to telegraph. Indian clubs do not have such a limitation

-a martial approach tends to focus on a tight, efficient motion with no superfluous movement. Club swinging can have more variety in this way. Wide swinging motions can be used.

-when used in pairs, clubs can be swung in complimentary and antagonistic ways. The antagonistic ones really open up the chest and shoulders. I haven't experienced this in FMA.

There are people like me who do FMA and Indian clubs, and some will combine them together with heavy sticks. One of the DBMA guys I see every blue moon does Indian club exercises with his heavy sticks to warm up and help rehab his shoulder (which I injured a year ago with a vertical downward strike and now I feel awful when I hear about his recovery process).

Kamagong looks pretty and is heavy that is about it. I've had kamagong snap on me, even just swinging in the air, with enough force, let alone hitting anything. Though, to put things into perspective, sticks in general were the padded/safety weapons of yesteryear, before things like padded sticks were invented. Arnis/Esrkima was a bladed art, and people needed a way to spar without necessarily killing each other, so indigenous woods were used. Hardwoods were often used in areas where it was easier to get than rattan, though rattan has far more give and is more forgiving on the body.

Filipinos dont fight with sticks when they truly want to kill. Go to Leyte/Samar, and you will still see how they fight when they want to do that, and that is with sharp swords/bolos. Again, wood/rattan for training or for looks, and the fancier the look the more its probably just for looks. As for weighted training, your average sansibar/sword will make a kamagong stick feel like paper, so would suggest if you are looking for heavier training tools, may as well use a real weapon your art was based on (no aluminum trainers they are far too light).